Add Twitter and Open Graph metadata cards

[TenType]

Example: when we post a link to a cmu.guide article on discord, it should display an embed containing the title and description

Code will look similar to this:

<!-- Open Graph / Facebook -->
<meta property="og:type" content="website" />
<meta property="og:url" content={Astro.url} />
<meta property="og:title" content={title} />
<meta property="og:description" content={description} />
<meta property="og:image" content={new URL(image.src, Astro.url)} />

<!-- Twitter -->
<meta property="twitter:card" content="summary" />
<meta property="twitter:url" content={Astro.url} />
<meta property="twitter:title" content={title} />
<meta property="twitter:description" content={description} />
<meta property="twitter:image" content={new URL(image.src, Astro.url)} />

[cytronicoder]

I think with #34 I have set up pretty much a good metadata system to cobble together something for this